Distribution centers experience increased demands as the number of goods shipped per unit of time increases. Typically, the infrastructure of distribution centers is relatively fixed, allowing for only marginal increases in throughput capacity without substantial investment in capital improvements.
For example, a distribution center may enhance throughput of existing systems by increasing the speed of conveyors and sorters, but only to a limited extent due to constraints such as conveyor belt size and strength, the momentum of moving items, and the configuration and location of sorting binds. Likewise, a distribution center may extend its operation but at substantial increase in operating costs including hours of labor and energy costs. Faced with these choices, distributors often build larger facilities to handle these increased demands. In addition to the obvious transactional costs associated therewith, including real estate acquisition and construction expenses, these bigger facilities impose larger fixed overhead costs that reduce profits, especially in times of decreased demand or fluctuations in supply.
Common sorting methods include bringing disparate items to a common location where sorting functions are carried out in a series of steps. Though the precise nature of existing sorting systems may be highly individualized, they generally require a discrete destination for each group or compound group of items. These discrete destinations usually involve a chute or a bin, among others. For example, if a distribution center needs to sort items into one thousand separate “groupings” of items (also referred to as “orders”), the system may include one thousand different discrete sorting destinations.
As shipping demands increase, the need for distribution centers with even greater capacity increases accordingly. The physical size of such buildings is substantial, challenging the capital resources of even the largest distributors. Such demands test the limits of complexity and logistical capacities of existing sorting technologies as well. Equipment needed to transport final groupings to downstream processes further increase as the quantity of sorting destinations increase. Transporting groupings from upstream to downstream locations in a continuous, sequential manner is not always possible, especially in larger systems. Moreover, the rates and timing of upstream processing are often poorly synchronized with downstream processes, necessitating buffer stations at various accumulation points throughout the distribution center.
Accordingly, it is desirable to reduce the number of sorting destinations while maintaining high throughput. One method of reducing the number of sorting destinations is to introduce an intermediate or secondary sorting step. In conventional systems employing such methods, an intermediate sorting stage tends to decrease the number of sorting destinations in of the system. As an example, consider a distribution center for sorting various items into one thousand predetermined groups of items (“orders”). An intermediate sort could be implemented at a first sorting station to sort the items into 20 compound groups at 20 sorting destinations, with each compound group containing 50 orders. Each of the 20 compound groups could thereafter undergo an additional sorting step in which the compound groups are sorted into 50 order groups at 50 sorting destinations. This exemplary system could accomplish a thousand group sort with only 70 total sorting destinations (20+50=70).
Prior attempts to introduce multiple sorting steps have revealed several drawbacks, especially if it is presumed that entropy must be reduced to the fullest practical extent at each shorting step. Consequently, these systems typically strive to maintain absolute discretion between the sorted groups or subgroups. That is, conventional systems do not allow intermixing between sorted groups. This requirement for absolute discretion places many restraints upon system configuration and flexibility, thereby decreasing system efficiencies.
Further system limitations also tend to minimize the attractiveness of intermediate sort processing. Reductions in capital equipment realized from intermediate sorting tends to be at least partially offset by an increase in the hardware required to transport the goods between the sorting stations. Additionally, bottlenecking tends to occur at downstream sorting destinations when previously sorted groups are not transported away as fast as upstream processes are able to replenish their supply. In this regard, such systems tend to require added sorting destinations or large amounts of buffering or accumulation equipment to compensate for these timing problems.
Accordingly, an improved system for sorting and distributing discrete items into large quantities of unique groups is desired.